Studies on the expression of human tRNA and rRNA-like genes were continued. Utilizing an in vitro mutagenesis method developed in our laboratory, both CtoT and G to A point mutants of the human tRNA(met) gene were generated. With these mutant genes we have explored the strructural requirements of the tRNA nuclear transport mechanism, as well as the two nuclear processing nucleases involved in the biosynthesis of the human tRNA(met) species. We have shown, using micro-injection into the nuclei of intact X laevis oocytes that both the processing enzymes as well as the nuclear transport system handle all mutant forms of tRNA(met) less efficiently than the wold-type. The most surprising result is that mutations within the anti-condon loop have profound effects on tRNA transport, suggesting that proteins which interact with specific tRNA species, such as the aminoacyl tRNA synthetase, may participate in tRNA transport. Biochemical studies of the two processing nucleases continue. Studies on the Alu-family sequence, a small, ubiquitous gene present in the vertebrate genome have been extended. We had shown that a particular Alu is transcribed, processed, and transported into the cytoplasm after nuclear injection of the gene into the oocyte. We have now found that this pathway is expressed in a tissue-specific fashion, suggesting for the first time a role for the Alu sequence in specific gene expression.